Technical Field
The invention relates to wheel end assemblies, and in particular to wheel end assemblies for heavy-duty vehicles, such as tractor-trailers. More particularly, the invention is directed to a main seal or hub seal for a heavy-duty vehicle wheel end assembly that extends radially between a hub of the wheel end assembly and an axle spindle, which prevents contaminants from entering the wheel end assembly and retains lubricant in the wheel end assembly. Still more particularly, the invention relates to a main seal for a heavy-duty vehicle wheel end assembly that includes external features and internal features that optimize the prevention of contaminants from entering the wheel end assembly and retain lubricant in the wheel end assembly, and provide a dynamic expulsion surface to expel any contaminants, while including minimal drag in order to preserve the life of the seal and optimize vehicle fuel efficiency.
Background Art
For many years, the heavy-duty vehicle industry has utilized wheel end assemblies which typically are mounted on each end of one or more non-drive axles. Each wheel end assembly typically includes a hub rotatably mounted on a bearing assembly that in turn is immovably mounted on the outboard end of the axle, commonly known as an axle spindle. As is well known to those skilled in the art, for normal operation of the wheel end assembly to occur, the bearing assembly and surrounding components must be lubricated with grease or oil. Therefore, the wheel end assembly must be sealed to prevent leakage of the lubricant, and also to prevent contaminants from entering the assembly, both of which could be detrimental to its performance. More specifically, a hubcap is mounted on an outboard end of the wheel hub, and a main seal or hub seal is rotatably mounted on an inboard end of the hub and the bearing assembly in abutment with the axle spindle, resulting in a closed or sealed wheel end assembly.
While most wheel end assemblies include these general features, the design and arrangement of the hub, bearing assembly, hubcap, main seal, and other components, as well as the axle spindle, vary according to the specific vehicle design and its anticipated uses. For example, main seals of the prior art have included non-contact types and contact types. More particularly, because the wheel hub is a dynamic component that rotates about the static axle spindle, the main seal bridges the gap between a dynamic environment and a static environment. As a result, in addition to retaining lubricant in the wheel end assembly and preventing contaminants from entering the wheel end assembly, it is desirable for a main seal to include minimal drag or friction between its internal components, thereby preserving the life of the seal and also increasing the fuel efficiency of the vehicle.
In order to reduce drag, non-contact seals were developed in the prior art. Non-contact seals include internal components that do not contact one another, and employ projections and specific geometric configurations to retain lubricant in the wheel end assembly and prevent contaminants from entering the wheel end assembly. However, while often desirably reducing drag, the non-contact nature of the components of such seals have not optimized the prevention of contaminants entering the wheel end assembly, at times resulting in the possibility of reduced life of the wheel end assembly.
In order to increase the ability of a main seal to prevent contaminants from entering a wheel end assembly, contact-type seals have been employed, which include internal components that contact one another to provide enhanced sealing characteristics. However, while generally providing improved exclusion of contaminants when compared to non-contact seals, prior art contact-type seals lack enhanced combinations of contaminant-exclusion features. Without such combinations of features to decrease the amount of contaminants that enter the structure of the seal, contaminants may eventually build up and bypass the contact components in the seal, thus contaminating the wheel end assembly and reducing its life.
As a result, there is a need in the art to develop a main seal for a heavy-duty wheel end assembly that provides features having increased contaminant exclusion, while retaining lubricant in the wheel end assembly and including minimal drag to preserve the life of the seal and optimize fuel efficiency. The main seal for a heavy-duty vehicle wheel end assembly of the present invention satisfies this need.